tjennette@thomasnelson.com (Trace) writes:
> Can someone please tell me what this previously-written SQL is doing?
> I don't understand how it is structured.
Apparently whoever wrote this doesn't believe in parentheses. I'd think
it a lot more readable with parentheses and appropriate indentation,
viz:
FROM ( (eStoreManager.estore_dept_prod LEFT OUTER JOIN eStoreManager.estore_product ON
eStoreManager.estore_dept_prod.sku= eStoreManager.estore_product.sku) RIGHT OUTER JOIN
(eStoreManager.tblCProductClassLEFT OUTER JOIN eStoreManager.tblCProductClassProduct ON
eStoreManager.tblCProductClass.ProductClassID= eStoreManager.tblCProductClassProduct.ProductClassID) ON
eStoreManager.estore_product.sku= eStoreManager.tblCProductClassProduct.sku)
FULL OUTER JOIN (eStoreManager.tblCProductClassCreator INNER JOIN eStoreManager.tblCCreator ON
eStoreManager.tblCProductClassCreator.CreatorID= eStoreManager.tblCCreator.CreatorID)
ON eStoreManager.tblCProductClass.ProductClassID = eStoreManager.tblCProductClassCreator.ProductClassID
BTW, since Postgres doesn't have schemas you'd need to lose the
"eStoreManager." prefixes, which aren't doing anything for readability
here either:
FROM ( (estore_dept_prod LEFT OUTER JOIN estore_product ON estore_dept_prod.sku = estore_product.sku) RIGHT OUTER
JOIN (tblCProductClass LEFT OUTER JOIN tblCProductClassProduct ON tblCProductClass.ProductClassID =
tblCProductClassProduct.ProductClassID) ON estore_product.sku = tblCProductClassProduct.sku)
FULL OUTER JOIN (tblCProductClassCreator INNER JOIN tblCCreator ON tblCProductClassCreator.CreatorID =
tblCCreator.CreatorID)
ON tblCProductClass.ProductClassID = tblCProductClassCreator.ProductClassID
Does that help any?
If you're wondering how I knew where to put the parentheses, it's
because there's no place else they could go and still have a
syntactically valid statement. So I suppose the author felt they
were unnecessary. But I think it's more readable with 'em.
regards, tom lane